Gas-blast electric circuit-breaker having contact fingers biased against auxiliary contact after disengagement from throat contact



Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINSTAUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT Filed Feb. 24.1961 7 Sheets-Sheet l FIG.1

Oct.12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINSTAUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT Filed Feb. 4,19"" 0.1. 7 Sheets-Sheet 2 j SE Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINSTAUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT 7 Sheets-Sheet3 Filed Feb. 24. 1961 FIG. 3

GONEK 'ETAL GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERSOct. 12, 1965 s. M.

BIASED AGAINST AUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT7 Sheets-Sheet 4 Filed Feb. 24, 1961 ol llwl ll.

FIG. 4

FIG. 6

Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINSTAUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT Filed Feb. 24,1961 7 Sheets-Sheet 5 FIG. 5

Oct. 12, 1965 s. M. GONEK ETAL 3,211,869

GAS-BLAST ELECTRIC CIRCUIT-BREAKER HAVING CONTACT FINGERS BIASED AGAINSTAUXILIARY CONTACT AFTER DISENGAGEMENT FROM THROAT CONTACT 7SheetS-Sheet6 Filed Feb. .24, 1961 S. M. GONEK ETAL Oct. 12, 1965 GAS-BLAST ELECTRICCIRCUIT-BREAKER HAVING CONTACT FINGERS 7 Sheets-Sheet 7 Filed Feb. .24.1961 age 1 31 i IL 9 m 0 F 8 2 w 4 mm d 9 V' M C N 8 84 a a? 8 Q 2, f 91 J l J 0 Q wu A/ United States Patent 3,211,869 GAS-BLAST ELECTRICCIRCUIT-BREAKER HAV- ING CONTACT FINGERS BIASED AGAINST AUXILIARYCONTACT AFTER DISENGAGE- MENT FROM THROAT CONTACT Stanislaw MieczyslawGonek and Henry Rowlinson, Stafford, England, assignors to The EnglishElectric Company Limited, London, England, a British company Filed Feb.24, 1961, Ser. No. 91,459 14 Claims. (Cl. 200-448) This inventionrelates to gas-blast electric circuitbreakers, that is to say tocircuit-breakers of the kind in which means are provided for causing ablast of gas, usually air, to pass between the co-operating surfaces ofthe interrupter contacts, as they are separated to effect an openingoperation of the circuit-breaker, so as to maintain the dielectricstrength of the medium between the contacts at a high value and therebyto assist in extinguishing any are formed between the contacts wheninterrupting a current.

According to the invention, a gas-blast circuit-breaker includescooperating first and second main contact members relatively movablebetween engaged and disengaged positions, one said main contact memberhaving a plurality of contacts individually biased when the main contactmembers are in their engaged position int-o engagement with a contactface of the other main contact memher; and an auxiliary contact membercapable of limited movement relative to the first main contact memberand arranged so that during an opening operation the cooperating contactsurfaces of the main contact members separate before those of the secondmain contact member and the auxiliary contact member, to which the loadcurrent is transferred from the first main contact member and which isat least temporarily biased towards the second main contact member, ablast of gas which is passed between the co-operating contact surfacesof the second main contact member and the auxiliary contact member asthey subsequently separate being passed in its passage through thecontact region first between the cooperating contact surfaces of themain contact members and subsequently between those of the second maincontact member and the auxiliary con-tact member. Both the maincontactmembers preferably have a generally tubular formation, the auxiliarycontact member sliding within the bore of the first main contact memberand the gas blast being exhausted through the second main contactmember.

In a circuit-breaker according to the invention, two or more pairs ofinterrupting contacts may be provided, each pair of contacts, togetherwith the enclosure, valves and other components peculiar thereto,constituting a circuit interrupter. Components of the circuit-breakersuch as support insulators and a compressed gas receiver may be commonto all the interrupters of the circuitbreaker.

The foregoing and other features of the invention will be evident fromthe following description, with reference to the accompanying drawingsof various air-blast circuit interrupter constructions embodying thefeatures of the invention in their preferred forms.

In the drawings, FIGS. 1, 2 and 3 are longitudinallysec-tioned views ofan interrupter construction, showing the contacts in their closed,arcing and isolated positions respectively,

FIG. 4 is an enlarged view of the contacts of the same interrupter intheir arcing position,

FIG. 5 is a detail of an alternative base arrangement,

FIGS. 6 and 7 show an alternative contact arrangement with the contactsrespectively in their closed and arcing positions, and

3,211,869 Patented Oct. 12, 196? FIGS. 8 and 9 arelongitudinally-sectioned views, with the contacts respectively in theirclosed and arcing positions, of an alternative interrupter construction.

The supporting structure of the interrupter shown in FIG. 1 comprises ahollow cylindrical insulator 10 mounted on a base cast-ing 11 andforming an enclosure 10a. Vertical mounting is assumed for convenience,but the interrupter is suitable for mouting in any position. A top capassembly 12 provides one electrical connection to the interrupter, asindicated at 13, the other being made at 14 to the base casting. Aflange 15 in the base casting is provided for connection to a source ofcompressed air, not shown in the drawing.

The interrupter contacts comprise a main fixed throat contact 16,forming part of and depending from the top cap assembly 12, and acomposite moving contact assembly 17. The latter includes a tubular maincontact member 18 which is divided at its upper end by a series oflongitudinal cuts to form a series of contact fingers 19, biasedinwardly by means of circular garter springs 20. In the closed positionof the interrupter, as shown in FIG. 1, the upper ends of theinwardly-directed cont-act surfaces 19a of the contact fingers 19 engagea corresponding contact surface 16a on the outer circumference of thethroat contact 16. Further contact fingers 21,.forming part of the basecasting 11 and outwardly biased by a spring 22, provide the electricalconnection between the moving cont-act assembly 17 and the base casting.f

The moving contact assembly 17 is mounted for limited sliding movementin the base casting 11, its movement being controlled by the selectiveadmission of compressed air to either the upper or the lower side of apiston 23 attached to the lower end of the tubular contact merr ber 18;.An annular blast valve 24 forming part of the moving contact member 17co-operates with an annular seating 25 to control the admission ofcompressed air to the annular passage 26 defined by the interiorsulfface of the insulator 10 and the outside of the movingc-ontactassembly 17.

The moving cont-act assembly 17 also includes an auxiliary arcingcontact 27, mounted within the tubularspace defined by the contactfingers 19. of the movingcontact member and capable of limited slidingmovement relative to that member. A spring 28 biases the contactsurf-ace 27a of the arcing contact member 27 into contact, when theinterrupter is closed,-with a corresponding inner con; tact surface 16bof the throat contact 16. Themove ment of the arcing contact 27 relativeto the moving contact member 18 can be controlled by the admission ofcompressed air to a cylinder 29 formed in the moving contact member, inwhich .a piston 30 attached to the arcing contact 27 can slide.

In the absence of a supply of compressed air to the cylinderscontrolling the movement of the moving parts, the contacts are biasedtogether by springs 31 situated within the hollow main contact member18. In these conditions the blast valve 24 is closed on to its seating25.

The interrupter top cap assembly 12 carries, in addition to the fixedthroat contact 16 and its associated varcing probe 32, an exhaust valve33. This valve is normally biased by a spring 34 to the open positionshown in FIG. 1 but is capable of being moved so as to cooperate with anannular seating 35 in closing an annular exhaust passage 36 leading fromwithin the bore of the throat contact 16 to the outside atmosphere. Adelay valve 37 controls the movement of the exhaust valve 33, as willhereinafter be explained, in accordance with the variation in airpressure within the annular space 26 surrounding the interruptercontacts.

The operation of the interrupter will best be understood by consideringthe break-and-make operating sequence. FIG. 1 shows the interrupter inits closed state;

the current path through the interrupter is completed by the engagementof the contact surface 19a of the contact fingers -19 with the outercontact surface 16a of the throat contact 16, the blast valve 24 beingclosed and the exhaust valve 33 open. Compressed air from the supplyconnected to the flanged union 15 fills the space 38 below the blastvalve 24. The action of this air pressure on the blast valve 24 is tosupplement the upward biasing effect of the springs 31 on the movablecont-act member 18; in order to balance to some extent the effect ofthis pressure, compressed air is also supplied through the passage 39 tothe upper side of the piston 23, which has an area slightly less thanthat of the blast valve 24. The interior of the moving contact member18, and the cylinder of the arcing contact piston 30, are at this stageconnected to the atmosphere through passages 40 and 41 respectively, anda further passage 42 connects the lower end of the cylinder 43 in whichthe piston 23 slides with the atmospher'e. It will be understood that.althought the passages 39, 40, 41, 42 are shown emerging from the outersurface of the base casting 11, there to be connected to suitable valvegear for the admission of compressed air or for its evacuation to theatmosphere, this is done for convenience in explanation only, and inpractice the valve gear may be housed within the base casting'll.

An opening operation ofthe interrupter is initiated by tripping an airvalve tosupply compressed air through the passage 41 to the lower-sideof the arcing contact piston 30. Thissupplenients the effect of thespring 28 in providing contact pressure between the contact surface 27aof the arcing contact 27 and the inner contact surface 16b of the throatcontact, and by its reaction on the moving contact .member 18 overcomesthe pressure of the springs 31 and the effect of the unbalanced pressureon the blast valve 24 soa-s to cause the moving contact member 18 tomove downwards. A sliding union 44 in the passage41 permits thecontinuance of the supply of air to thecylinder 29v during thismovement. As soon as the movement of the moving contact member 17 liftsthe blastva'lve 24 from its seating 25, the pressure unbalance.acrossthe blast valve is removed and as a result the movement of themoving contact member is accelerated. During this initial movement ofthe moving cont-act member 18 the contact fingers 19 are withdrawn fromthe throat contact 16 and move inwardly under the biasing action of thegarter springs 20 to embrace and make confact with the cylindricalcontact surface 27b of the auxiliary contact 27, to which the currentthrough the interrupter is now transferred. The pressure differenceacross the arcing contact 27, in addition to the air pressure in thecylinder 29 and the action of the spring 28, ensures that the arcingcontact 27 remains pressed firmly in contact with the throat contact 16during this part of the operation.

As the movement of the moving contact member 18 continues, the arcingcontact 27 reaches the limit of its travel relative to it. Furthermovement of the moving contact member 18 carries with it the arcingcontact 27 and hence separates the contact surfaces 27a, 16b of thearcing contact and of the throat-contact, permitting the flow of thefull air blast through the interrupter; when the movement of the movingcontact assembly is complete the contacts are in the relative positionshown in FIG. 2. The movement of the contacts may be buffered by theaction of the piston 23 within its cylinder 43 and of the arcing contactpiston 30 within its cylinder 29. During this part of the operation anarc is drawn between the arcing {contact 27 and the throat contact 16,being transferred to the arcing probe 32 within the throat contact bythe blast of gas which flows through the open blast valve and to theatmosphere through the bore 160 of the throat contact and the openexhaust valve 33. On the opening of the blast valve 24 and thesubsequent filling of the interior enclosure a of the insulator 10 withair under pressure, air is fed through a passage 45 to the delay 4 valve37, which after an interval long enough to ensure the extinction of theare drawn between the contacts applies compressed air to the upper sidesof the piston 46 formed in the exhaust valve 33 and causes the exhaustvalve to move to its closed position. Finally, the passage 41 isexhausted to the atmosphere and the arcing contact 27 moves under theaction of the air pressure in passage 26 acting on the upper side ofpiston 30, to the retracted position shown in FIG. 3, thus providing acontact gap of adequate electrical strength, even at atmos= pheric airpressure, to obviate the provision of a separate series or isolatingswitch. The interior enclosure 10a of the insulator 10 remains full ofair under pressure.

In order to return the interrupter to its closed position compressed airis simultaneously applied to the cylinder 29 through the passage 41, tothe lower end of the cylinder 43 through the passage 42, and to thelower side of the exhaust valve piston 46 through a passage not shown inthe drawing. Thus the. arcing contact 27 is'returned to the positionshown in FIG. 2, projecting beyond the end of the tube defined by thecontact fingers 19; the exhaust valve 33 is opened to allow a blast ofair to pass through the circuit-breaker, and the moving contact assembly17 commences to move as a whole towards its closed position. As soon asthe contact surface 27a of the arcing con-tact 27 engages the innerarcing surface 16b of the throat contact 16, it acts as a valve tointerrupt the air blast. The air pressure which as a result builds up inthe annular space 26 surrounding the contacts causes the arcing contact27 to be pressed firmly against the contact surface 16b of the throatcontact. As the movement of the moving contact member 18 continues, thesurfaces 19a of the contact fingers 19 engage the outer surface 16a ofthe throat contact and disengage from the arcing contact 27, thustransferring the current to the main contact surfaces 19a, 16a. Finallythe blast valve 24 engages its seating 25and cuts off the supply of airto the interior enclosure 10a of the insulator. The air trapped thereinis allowed to escape by means of a bleed passage 47 communicating withthe interior of the throat contact 16 and thence with the atmosphere,the exhaust valve 33 remaining open.

As the contacts approach each other, under live circuit conditions anarc may be struck between the arcing contact 27 and the throat contact16. The presence of the blast of air through the interrupter ensuresthat this are is immediately swept into the throat contact 16 andtransferred to the arcing probe 32, in the same manner as during anopening operation. The transfer of the current from the arcing contactto the contact fingers 19 of the moving contact member 18, which bear ona different contact surface 16a of the throat contact, ensures that themain current-carrying surfaces 19a, 16a are unaffected by arcing duringeither opening or closing operations.

FIG. 4 of the drawings shows an enlarged view of the interruptercontacts. It shows that the arcing contact 27 is built up from a bodymember 48, a central arcing insert 49 and an annular arcing face 50surrounding it and providing the contact surface 27a. An annular arcingring 51 is provided within the throat contact 16 and provides the innercontact surface 16b. On the formation of an arc between the contactseither during an opening or a closing operation, only the initialflashover is. carried by the outer arcing face 50 and the throatc-ontact arcing ring 51, the are being immediately transferred to thecentral arcing insert 49 and the arcing probe 32 of the throat contactand remaining there until subsequently extinguished at a current zero.

FIG. 4 also shows that in the relative positions of the contacts adoptedduring arcing conditions the profile of the composite moving contactassembly 17, being free from abrupt discontinuities, is such that theelectrical field intensity between the contacts is not therebyundulyraised. Furthermore the flow of compressed air over the contact surfacesto the interior of the throat contact 16 can occur as indicated by thearrows substantially without turbulence.

FIG. 5 shows a detail of a circuit-breaker in which two interrupters 52are mounted in opposed in-line formation on a common base casting 53.Each interrupter 52 is generally similar to the interrupter shown inFIGS. l-3, but the blast valves 24 shown in those figures are omitted,being replaced by a single sleeve-type blast valve 54 closing thecompressed air inlet to the base casting 53. This enables the length ofthe interrupter to be reduced, compared with the interrupter of FIGS.l3, and hence effects a considerable reduction in the length of thedouble interrupter assembly. The control of the interrupter becomes morecomplex, since the blast valve 54 has to be opened and closed insynchronism with the movements of the contacts and since the pressureunbalance across the blast valve 24 of FIGS. 1-3 can no longer beemployed to assist in controlling the movements of the contacts.

The blast valve 54 is controlled by the admission of compressed air tothe cylinder 55 in which slides an an nular piston 56 formed in the endof the blast valve. The annular face of the valve co-operates with anannular seating 57 in the base casting, this seating being recessed asshown to protect it from the blast of air. A deflector 58 helps toensure the free flow of air to the interrupters when the blast valve isopen.

An alternative contact arrangement, suitable for substitution for thecontact arrangements shown in FIG. 4 is illustrated in FIGS. 6 and 7 ofthe drawings. The contacts here shown comprise a throat contact 60 and acomposite second contact assembly 61. In the interrupter constructionshown in FIGURES l to 3, the throat contact 60 would be fixed and thesecond contact assembly 61 would move; but this arrangement could ofcourse be varied in the application of the contact arrangement shown inFIGS. 6 and 7 to other interrupter constructions.

The throat contact 60 is provided with an annular arcing ring 62, fittedwithin its throat aperture, and with a series of at least three contactfingers 63 spaced around the throat contact outside the arcing ring 62.The contact fingers 63 are generally L-shaped in radial section,

tion 63a fits into a corresponding groove 60a in the throat 'contact 60,which may consist of a series of grooves of cylindrical section, eitherconnected or separate. The

surfaces of the grooves 60a and of the end portion 63a of the contactfinger can thus slide over each other and allow the contact finger 63 tomove under the action of biasing springs 64. The large contact area thusprovided reduces the risk of the sliding contact surfaces becomingwelded together. A lip at the end of the lower arm of the contact finger63 engages a rim of the arcing ring '62 to limit the movement of thecontact finger.

The throat contact 60 is also provided with a central arcing probe 65within its bore 600.

The second contact assembly 61 comprises a generally cylindrical maincontact member 66 and an arcing contact member 67 arranged to slidewithin the end of the main contact member 66 between positions in whichit is at least partly retracted within the main contact member, as shownin FIG. 6, and in which it projects beyond the contact member, as shownin FIG. 7, to provide a composite contact surface so shaped that it doesnot cause the electrical field intensity between the main contactmembers 60 and 66 to be unduly high at any point and does not causelocal turbulence of the air blast.

The main contact member 66 terminates in an annular contact surface 66a,arranged to make butt contact with the contact surface 63b of thecontact finger 63 of the throat contact 60, contact pressure beingsupplied by the springs 64.

The arcing contact 67 is provided with an arcing ring 68, which has acontact surface 68a which, in the closed position of the contacts, makescontact with the contact surface 62a of the arcing ring 62 of the throatcontact and is also provided with a central arcing insert 69. A goodelectrical connection between the main contact member 66 and the arcingcontact 67 is ensured by the provision of contact strips and biasingsprings 70 between the two contact members. Movement of the arcingcontact 67 in relation to the main contact 66 is effected by supplyingcompressed air through a passage 71 to the lower side of the arcingcontact 67 and by exhausting this passage to the atmosphere. In additionbiasing springs, not shown in the drawing, may be employed.

Any are formed in operation is struck between the arcing rings 62 and68, but is swept by the air blast into the throat contact to beestablished between the probe 65 and the arcing insert 69 of the arcingcontact.

The interrupter construction shown in FIGS. 8 and 9 of the drawings isgenerally similar to that shown in FIGS. 1 to 3 but embodies certainfurther features and operates in a rather different manner.

The interrupter structure comprises a hollow insulator mountedvertically (although suitable for mounting at any other angle) by meansof a base casting 81 and having a top cap assembly 82; the base castingand the top cap assembly from the electrical connections to theinterrupter as indicated diagrammatically at 83 and 84 respectively. Thebase casting 81 is provided with a flanged joint 85 for connection to asupply of compressed air, which is in a permanent connection with theinterior enclosure 80a of the insulator 80.

The interrupter contacts comprise a movable throat contact 88 and acomposite contact assembly 89 consisting essentially of a tubular member90 supported from the base casting 81 (of which it may form part) so asto project into the insulator 80., At its upper end the contact member90 is divided by a series of longitudinal cuts to form a series of threeor more contact fingers 91, which are biased by circular garter springs92, and possibly also by their own resilience, towards the interior ofthe tube they define. An arcing contact member 93 'is mounted within thecontact fingers 91 so as to be capable of limited sliding movementbetween the position in which its tip is approximately in line with thetops of the contact fingers 91, as shown in FIG. 8 and that in which itprojects beyond the contact fingers 91 as shown in FIG. 9. A guidemember 94 terminating in a piston 95 is mounted on the contact member 90by means of a boss 96; the piston 95, sliding within the cylinder 97formed in the arcing contact 93, serves both to guide and control thearcing contact in its movement. A passage 98 which opens on to the uppersurface of the piston 95 is normally supplied with air under pressurebut can be exhausted to the atmosphere. A spring 99 biases the arcingcontact 93 outwardly from the contact member 90.

The throat contact 88 has a bore 88c and is arranged to slidelongitudinally within a support tube 100 formed as an extension of theinsulator top-cap base member 101. The lower end of the support tube 100is divided in the same way as that of the contact member 90 to form aseries of three or more contact fingers 102 inwardly biased by circulargarter springs 103. Webs 104 connect the throat contact 88 with a pistonrod 105, which at its upper end carries a piston 106 sliding within acylinder 107 in the top-cap cylinder block 108. The lower end of thepiston rod is extended downwards to form the arcing probe 109 of thethroat contact.

The choice of the throat contact 88 as the movable main contact of thecircuit-breaker simplifies the provision 110 will be in its upperposition. tains air under pressure.

.later be described. An annular piston 111 formed at the top of thevalve sleeve 110 controls the movements of the latter, which is upwardlybiased by springs 112 at its lower end.

A contact pressure spring 113 biases the throat contact 88 downwardlytowards engagement with the lower contact.

The interior of the throat contact 88 communicates with the atmosphereby means of an annular passage 114. An annular exhaust valve 115,sliding within an annular recess in the top-cap cylinder block 108, canco-operate with an'annular seating 116 in the top-cap base member 101 toclose the passage 114, being biased towards this position by a spring117. An annular piston 118 formed on the top of the exhaust valve member115 slides in a cylinder 119 to which compressed air can be supplied tocontrol the movement of the exhaust valve.

The valve gear by means of which the supply of air to the variouscylinders is controlled is not shown in the drawing, but it may take anyconvenient form and may be situated either within the circuit-breakerstructure or externally.

The operation of the interrupter will now be described by going througha break-an d-make cycle of operations.

In the closed position of the interrupter, shown in FIG. 8 of thedrawings, the inwardly-directed contact surfaces 91a of the contactfingers 91 of the lower contact member 90 engage a correspondingoutwardly-directed contact surface 88a of the throat contact 88. In thisposition the contact fingers 91 are forced apart so that they do notbear against the outer periphery of the arcing contact 93, the circuitthrough the circuit-breaker being completed solely by the contactfingers 91 and their co-operating contact surfaces on the throat contact88. The arcing contact 93 is, however, biased upwardly by its spring 99so that the contact surface 120a of an arcing ring 120 set into itssurface makes contact with the contact surface 121a of a correspondingarcing ring 121 within the aperture of the throat contact 88.

Before the commencement of an opening operation, the exhaust valve 115will be closed, and the sleeve valve The insulator 80 con- To initiatean opening operation of the interrupter, compressed air is suppliedthrough a connection 129 to the lower side of the exhaust valve piston118. The upper side of this piston being as indicated in permanentconnection with the atmosphere, the force of the valve closing spring117 is overcome and the exhaust valve 115 opens. The interior of thethroat contact 88 is thus vented to the atmosphere, but the engagingcontact surfaces of the throat contact and the arcing contact 93 act asa valve to prevent the flow of compressed air to the interior of thethroat contact, the effect of the difference in air pressure across thecontacts being to increase the contact pressure between the arcingcontact and the throat contact. This increase of contact pressure issufficient to overcome the force exerted by the throat contact pressurespring 113 and to cause the throat contact 88 to move upwards slightly.This allows a flow of compressed air to pass from the annular space 122surrounding the contacts to the lower face of the throat contact piston106 through the passage 123 to the top-cap cylinder block 108 andthrough the open sleeve-valve port 124, thereby accelerating the throatcontact 88 in an upward direction. The air trapped above the piston 106in the cylinder 107 is exhausted partly through a bleed aperture 126 andpartly through a further port 127 in the sleeve valve As the throatcontact 88 moves upward, it is disengaged from the contact fingers 91 ofthe lower contact member 90, which move inwardly to transfer the currentto the arcing contact 93, which is still being pressed against thethroat contact 88 by the combined action of the spring 99 and of the airpressure difference across the contacts. When the arcing contact 93reaches the end of its travel relative to the contact member 90, definedby the travel of the piston 95 within its cylinder 97, the contactsurfaces of the arcing contact 93 and of the throat contact 88 areseparated, and (if the circuit-breaker is carrying a current) an arc isdrawn between them. The separation of the contact surfaces has, however,allowed a blast of gas to fiow between them into the interior ofthethroat contact 88 and through the open exhaust valve to theatmosphere. The are is therefore swept into the throat contact 88, beingtransferred to the arcing probe 109 of the throat contact and thecentral arcing insert 128 of the arcing contact 93. Only the initialflash is thus carried by the arcing rings and 121 of the two contacts,and all the arcing products are swept into the throat contact and awayto the atmosphere.

As the piston 106 approaches the end of its travel, its periphery closesthe port 127 in the sleeve valve 110; the subsequent reduced rate ofescape of air from the cylinder 107 buffers'the movement of the throatcontact.

The condition of the interrupter when the moving contact asembly reachesthe limit of its stroke is shown in FIG. 9. It will be seen from thisfigure that the profile presented by the combined surfaces of the arcingcontact 93 and of the contact fingers 91 does not presentdiscontinuities which would raise the electrical stress in the spacebetween the contacts to an undesirable extent and which might result inlocal turbulent flow of the air blast between the contacts.

At a moment after the initiation of an opening operation by which anyare formed between the contacts will have been extinguished, a delayvalve, not shown in the drawings, vents the lower side of the exhaustvalve piston 118 to the atmosphere through the connection 129, and theexhaust valve closes under the action of its spring 117. The blast ofgas through the interrupter therefore ceases. At the same time thepassage 98 leading to the upper face of the arcing contact controlpiston 95 is exhausted to the atmosphere, and the air pressure on thearcing contact causes it to retract within the contact fingers 91, thusincreasing the gap between the opposed contact surfaces of thecircuit-breaker sufliciently to provide adequate electrical isolationwithout the use of a separate series isolating switch. The entireinterior of the insulator 80 remains full of air under pressure, and thedielectric strength of the medium between the opposed contact surfacesis therefore maintained at a high value.

With reference to this condition of the interrupter, it will be notedthat with the exhaust valve 115 in its closed position as shown in FIG.8, the pressure of the air within the insulator 80 exerts a differentialeffect on the valve member 115 and biases it towards its closedposition. This eifect is produced by the difference of the diameters ofthe annular exhaust valve seating 116 and the toroidal sealing memberpreventing air leakage past the upper part of the exhaust valve. Thuswhen the interrupter is open and the insulator 80 contains air underpressure, the exhaust valve 115 will be maintained in its closedposition, preventing loss of air from within the insulator, even thoughits biasing spring 117 should fail.

The seating 116 of the exhaust valve is housed within a recess in thelower wall of the annular exhaust passage 114; its surface is thereforeprotected from the hot gases and are products flowing past it duringoperation of the circuit-breaker.

These features of the exhaust valve and its seating could equally wellbe applied to the exhaust valve of the interrupters shown in FIGS. 1 to3 and in FIG. 5.

In order to initiate a closing operation of the interrupter, air underpressure is admitted through the passage 98 to the upper face of thepiston 95, restoring the arcing contact 93 to its projected position inrelation to the contact fingers 91. At the same time the exhaust valve115 is opened under the action of air pressure applied to the lower faceof the piston 118. A blast of air commences to flow through theinterrupter, which is then in the condition shown in FIG. 9. Also at thesame moment air is supplied through the connection 131 to the upper faceof the piston 111 formed at the top of the sleeve valve 110, forcing thesleeve valve to its lower position. This allows air under pressure toflow through the port 132 of the sleeve valve to the upper side of thethroat contact piston 106. The throat contact 88 therefore commences tomove downwardly, the air trapped below its piston being exhausted to theatmosphere through a further port 133 at the lower end of the sleevevalve 110 and through the open exhaust passage 114.

As the contacts approach each other, a point will be reached at whichthe electrical strength of the gap between them is less than thepotential difference between them. Owing to the blast of gas flowingbetween the contact surfaces, the dielectric strength of the interveningmedium will be high and the contacts will be very close to each otherbefore flashover in fact occurs between the arcing rings 120 and 121 ofthe two contacts. The are formed will be at once swept by the air blastinto the throat contact 88 and transferred to the central arcingsurfaces 128 of the arcing contact and the arcing probe 109 of thethroat contact. Further movement of the throat contact causes the arcingrings 120 and 121 to make contact,

short-circuiting and extinguishing the arc. Since the arcing contact 93is small and light, and is biased towards engagement with the throatcontact 88 both by means of the spring 99 and by means of the airsupplied under pressure to the upper face of its piston 95, rebound ismost unlikely to occur. Furthermore, on engagement of the contactsurfaces, these act as a valve to interrupt the flow of air through thecircuit-breaker, and the pressure dilference across the arcing contact93 ensures that the latter is pressed even more firmly against thethroat contact 88.

Continued movement of the throat contact causes the contact fingers 91of the lower member 90 to engage the contact surface 88a of the throatcontact, and the load current is transferred to these contact surfaces.

The closing operation now being completed, the exhaust valve 115 isallowed to close by venting the connection 129. The interrupter remainsfull of air at atmospheric pressure.

Finally the passage 131 is exhausted to the atmosphere to allow thesleeve valve 110 to return to its upper position in readiness for afurther opening operation.

The alternative contact arrangements described with reference to FIGS. 6and 7 for the interrupter of FIGS. 1 to 4 are equally applicable to theinterrupter of FIGS. 8 and 9.

What we claim as our invention and desire to secure by Letters Patentis:

1. A gas-blast electric circuit-breaker comprising first and secondcontact members, said contact members being relatively movable betweenengaged and disengaged positions, said second contact member having anexternal cylindrical contact surface, and said first contact memberhaving a plurality of contact fingers disposed in a ring, said fingersbeing individually biased in an inward direction transverse to thedirection of relative movement of said first and second contact membersso as to engage, when the first and second contact members are in theirengaged position, with said external cylindrical contact surface, anauxiliary contact member mounted on said first contact member withinsaid ring for limited movement relative to said first contact member andlaterally disposed with respect to and adjacent to said plurality ofcontact fingers, means at least temporarily to bias the auxiliarycontact member towards said second contact member whereby the auxiliarycontact member remains pressed firmly in contact with said secondcontact member during separation of said first and second contactmembers during opening operation of the circuitbreaker, and whereby onseparation of said plurality of contact fingers from said externalcylindrical contact surface during said opening operation said fingersmove to make contact with the auxiliary contact member.

2. A gas-blast electric circuit-breaker as claimed in claim 1 whereinsaid auxiliary contact member has an external cylindrical contactsurface with which said fingers make contact on separation from saidsecond contact member.

3. A gas-blast electric circuit-breaker comprising a first contactmember, a second contact member having a bore, an external cylindricalcontact surface surrounding the mouth of said bore, and an internalannular contact surface within said mouth, said contact members beingrelatively movable between engaged and disengaged positions, meansdefining an exhaust passage leading from said bore at least temporarilyto atmosphere, said first contact member having a plurality of contactfingers individually biased in an inward direction transverse to thedirection of relative movement of said first and second contact membersso as to engage, when the first and second contact members are in theirengaged position, with said external cylindrical contact surface, anauxiliary contact member mounted on said first contact member forlimited movement relative thereto, laterally disposed with respect toand adjacent to said plurality of contact fingers, and having an annularcontact surface, means at least temporarily to bias the auxiliarycontact member towards said second contact member whereby the annularcontact surface of the auxiliary contact member remains pressed firmlyin contact with said internal annular contact surface of the secondcontact member during separation of said first and second contactmembers during opening operation of the circuit-breaker, and whereby onseparation of said plurality of contact fingers from said externalcylindrical contact surface of said second contact member during saidopening operation said plurality of contact fingers moves to makecontact with the auxiliary contact member, wall means defining anenclosure within which said first and second contact members aresituated, and means to supply gas under pressure to said enclosureduring opening operation of the circuit-breaker whereby when saidauxiliary contact member separates from said second contact member ablast of gas passes first between the co-operating contact surfaces ofsaid first and second contact members and subsequently between those ofthe second main contact member and the auxiliary contact member.

4. A gas-blast electric circuit-breaker comprising a first contactmember, a second contact member having a bore, said contact membersbeing relatively movable between engaged and disengaged positions, meansdefining an exhaust passage leading from said bore to atmosphere, anauxiliary contact member mounted within said first contact member forlimited movement relative thereto projecting from said first contactmember, and adapted to make sealing contact with said second contactmember, wall means defining an enclosure within which said first andsecond contact members are situated, means to supply gas under pressureto said enclosure during at least part of a closing operation of thecircuit-breaker, and means to cause relative movement of said first andsecond contact members towards one another until said auxiliary contactmember makes sealing contact with said second contact member, wherebyprior to making of said sealing contact said gas escapes through saidbore in said second contact member and after making of said sealingcontact further escape of gas is prevented, and further including ablast valve controlling admission of gas to said enclosure, and formingpart of said first contact member,whereby said blast valve opens asSald'fiISt contact member moves from an engaged position to a disengagedposition.

5. A gas-blast electric circuit-breaker including a circuit interrupterhaving three co-operating interrupter contacts, namely a first maincontact, a second main contact, and an auxiliary contact, said firstmain contact having a fixed tubular base and having its end divided toform a series of contact fingers integral with said fixed tubular base,said contact fingers being biased inwardly and being formed withinwardly-directed contact surfaces, said second main contact beingmoveable, having a hollow bore, an aperture of which opens towards sa1dfirst main contact, and being formed with an outwardly- .directedcylindrical contact surface and with an arcing contact surfacesurrounding said aperture, said auxiliary contact being slidably mountedon said first main contact, concentrically with said contact fingers,for movement between a first position in which it projects beyond saidcontact fingers and a second position in which it is substantiallywithin said contact fingers, said auxiliary contact being formed with anarcing contact surface to cooperate with the arcing contact surface ofsaid second main contact and with an outwardly-directed cylindricalcontact surface of smaller diameter than the cylindrical contact surfaceof said second main contact, said circuitbreaker also comprising meansurging said auxiliary con- .tact to said first position, whereby in theclosed position of the interrupter the inwardly-directed contactsurfaces of said contact fingers engage the outwardly-directedcylindrical contact surface of the second main contact and .are'radiallyspaced from the outwardly-directed cylindrical contact surface of saidauxiliary contact, and the arcfirst main contact before it separatesfrom the auxiliary contact, said contact fingers moving inward afterdisengagement from said outwardly-directed cylindrical contact surfaceof said second main contact to make contact with the outwardly-directedcylindrical contact surface of' said auxiliary contact, therebytransferring the current to the latter..

6. A gas-blast electric circuit-breaker as claimed in claim 5,comprising also means enclosing said interrupter contacts to definean'enclosure surrounding said interrupter contacts, compressed gassupply means in permanent connection with said enclosure, and meansconnecting said hollow bore of the second main contact at leasttemporarily to atmosphere during opening of said circuit interrupter,whereby during opening of said circuit interrupter a blast of gas passesfrom said compressed gas supply means, through Said enclosure, betweensaid contact fingers and said second main contact, and then between thearcing contact surface of the second main contact and the arcing contactsurface of the auxiliary contact into said hollow bore and thence toatmosphere. 7. A gas-blast electric circuit-breaker as claimed in claim6, comprising also an arcing probe within said hollow bore of the secondmain contact, whereby, when "swept into said hollow bore by said blastand thus to atmosphere.

8. A gas-blast electric circuit-breaker including a circuit interrupterhaving three co-operating interrupter contacts, namely a first maincontact, a second main contact, and an auxiliary contact, said firstmain contact having a fixed tubular base and having its end divided toform a series of contact fingers integral with said fixed tubular base,said contact fingers being biased inwardly and being formed withinwardly-directed contact surfaces, said second main contact beingmoveable, having a hollow bore, an aperture of which opens towards saidfirst main contact, and being formed with an outwardlydirectedcylindrical contact surface and with an arcing contact surfacesurrounding said aperture, said auxiliary contact being slidably mountedon said first main contact, concentrically with said contact fingers,for movement between a first position in which it projects beyond saidcontact fingers and a second position in which it is substantiallywithin said contact fingers, said auxiliary contact being formed with anarcing contact surface to co-operate with the arcing contact surface ofsaid second main contact and with an outwardly-directed cylindricalcontact surface of smaller diameter than the cylindrical contact surfaceof said second main contact, said circuitbreaker also comprising meansurging said auxiliary contact to said first position relative to saidfirst main contact, including resilient means abutting both saidauxiliary contact and said first main contact, whereby during closing ofsaid circuit interrupter firstly the arcing contact surface of saidauxiliary cont-act engages the arcing contact surface of said secondmain contact and later the inwardly-directed contact surfaces of thecontact fingers engage the outwardly-directed cylindrical contactsurface of the second main contact and disengage from thesmaller-diameter outwardly-directed cylindrical contact surface of theauxiliary contact, any are which is drawn being struck between saidarcing contact surfaces.

9. A gas-blast circuit-breaker comprising a circuit interrupter havingthree co-operating interrupter contacts, namely a first main contact, asecond main contact, and an auxiliary contact, said first main contacthaving a fixed tubular base and having its end divided to form a seriesof contact fingers intergral with said fixed tubular base, said contactfingers being biased inwardly and being formed with inwardly-directedcontact surfaces, said second main contact being moveable, having ahollow bore, an aperture of which opens towards said first main contact,and being formed with an outwardly-directed cylindrical contact surfaceand with an arcing contact surface surrounding said aperture, saidauxiliary contact being slidably mounted on said first main contact,concentrically with said contact fingers, for movement be tween a firstposition in which it projects beyond said contact fingers and a secondposition in which it is substantially within said contact fingers, saidauxiliary contact being formed with an arcing contact surface tocooperate with the arcing contact surface of said second main contactand with outwardly-directed cylindrical contact surface of smallerdiameter than the cylindrical contact surface of said second maincontact, said circuitbreaker also comprising means urging said auxiliarycontact to said first position, said circuit-breaker comprising alsomeans enclosing said interrupter contacts to define an enclosuresurrounding said interrupter contacts, compressed gas supply means inpermanentconnection with said enclosure, an exhaust valve connected tosaid hollow bore to control the outlet of gas therefrom, bias means tobias said exhaust valve to the closed position, means to cause relativemovement of said second main contact away from said first main contactand from said aux- 1liary contact to an open position of theinterrupter, and means to open said exhaust valve during said relativemovement to allow a blast of gas to flow between the contacts into saidhollow bore and through the open exhaust valve to atmosphere, said biasmeans causing the exhaust valve to reclose so that said enclosureremains full of air under pressure whereby to provide adequateelectrical isolation without the use of a separate series isolatingswitch.

10. A gas-blast electric circuit-breaker including a circuit interrupterhaving three co-operating interrupter contacts, namely a first maincontact, a second main contact, and an auxiliary contact, said firstmain contact having a fixed tubular base and having its end divided toform a series of contact fingers integral with said fixed tubular base,said contact fingers being biased inwardly and being formed withinwardly-directed contact surfaces, said second main contact beingmoveable, having a hollow bore, an aperture of which opens towards saidfirst main contact, and being formed with an outwardlydirectedcylindrical contact surface and with an arcing contact surfacesurrounding said aperture, said auxiliary contact being slidably mountedon said first main contact, concentrically with said contact fingers,for movement between a first position in which it projects beyond saidcontact fingers and a second position in which it is substantiallywithin said contact fingers, said auxiliary contact being formed with anarcing contact surface to cooperate with the arcing contact surface ofsaid second main contact and with an outwardly-directed cylindricalcontact surface of smaller diameter than the cylindrical contact surfaceof said second main contact, said circuitbreaker also comprising meansurging said auxiliary con tact to said first position relative to saidfirst main contact including resilient means abutting said auxiliarycontact and said first main contact, piston-and-cylinder meanscomprising a piston element and a co-operating cylinder element, onesaid element being structurally united with said auxiliary contact andthe other said element being structurally united with said first maincontact, for slidably mounting said auxiliary contact on said first maincontact, means enclosing said interrupter contacts to define anenclosure surrounding said interrupter contacts, compressed gas supplymeans in permanent connection with said enclosure, said circuit-breakerfurther comprising fixed structure including a support tube and cylindermeans, said second main contact being mounted in said support tube toslide longitudinally therein, a .piston rod within the hollow bore ofsaid second main contact, webs connecting said second main contact withsaid piston rod, piston means connected to said piston rod and slidablymounted in said cylinder means, means to supply gas under pressure tosaid cylinder means to actuate said piston means to move said secondmain contact between open and closed positions of said circuitinterrupter, said fixed structure defining passage means communicatingat least temporarily between the interior of said support tube andatmosphere, whereby a blast of gas flowing between the contacts andthrough said hollow bore may pass between said webs, through saidsupport tube and through said passage means to atmosphere irrespectiveof the position of said second main contact.

1 1. A gas-blast electric circuit-breaker as claimed in claim comprisingalso an annular exhaust valve mounted in said fixed structure andmoveable between a first position in which the interior of said supporttube communicates freely with atmosphere and a second position in whichsaid passage means is closed, bias means to bias said exhaust valve tosaid second position, said fixed structure also including a cylinder, apiston mounted to slide in said cylinder and structurally united withsaid exhaust valve, and further comprising means to supply gas underpressure to said cylinder to overcome said bias means and move saidannular exhaust valve to said first position.

12. A gas-blast electric circuit-breaker as claimed in claim 11comprising also a communication between said cylinder means and saidpassage means upstream of said annular exhaust valve, whereby on openingof said annular exhaust valve said cylinder means is vented toatmosphere and the force loading said piston means in the sense ofclosing said circuit interrupter is reduced.

13. A gas-blast electric circuit-breaker including a circuit interrupterhaving three only co-operating interrupter contacts, namely a first maincontact, an auxiliary contact slidably mounted on said first maincontact, and a sec-ond main contact movable relative to said first maincontact and to said auxiliary contact between engaged and disengagedpositions, said first main contact having a tubular base and having itsend divided to form a series of contact fingers integral with saidtubular base, said contact fingers being biased inwardly and beingformed with inwardly-directed contact surfaces, said second main contactbeing formed with a first outwardlydirected cylindrical contact surfaceand with a first arcing contact surface, said auxiliary contact beingformed with a second arcing contact surface to co-operate with saidfirst arcing contact surface and being formed with a secondoutwardly-directed cylindrical contact surface which is of smallerdiameter than said first outwardly-directed cylindrical contact surfaceand which is substantially within and surrounded by said contactfingers, and means urging said auxiliary contact towards said secondmain contact, whereby during opening of said interrupter saidinwardly-directed contact surfaces separate from said firstoutwardly-directed cylindrical contact surface before said first arcingcontact surface separates from said second arcing contact surface, andsaid contact fingers move inward so that the inwardly-directed contactsurfaces engage said second outwardly-directed cylindrical contactsurface.

14. A gas-blast electric circuit-breaker comprising a first contactmember, a second contact member having a bore, said contact membersbeing relatively movable between engaged and disengaged positions, meansdefining an exhaust passage leading from said bore to atmosphere, anauxiliary contact member mounted within said first contact member forlimited movement relative thereto projecting from said first contactmember, and adapted to make sealing contact with said second contactmember, wall means defining an enclosure within which said first andsecond contact members are situated, means to supply gas under pressureto said enclosure during at least part of a closing operation of thecircuit-breaker, and means to cause relative movement of said first andsecond contact members towards one another until said auxiliary contactmember makes sealing contact with said second contact member, wherebyprior to making of said sealing contact said gas escapes through saidbore in said second contact member and after making of said sealingcontact further escape of gas is prevented, and exhaust valve meansdisposed in said exhaust passage, whereby opening of said exhaust valvepermits gas under pressure in said enclosure to escape therefrom throughsaid bore.

References Cited by the Examiner UNITED STATES PATENTS BERNARD A.GILHEANY, Primary Examiner.

MAX L. LEVY, E. JAMES SAX, ROBERT K. SCHAE- FER, Examiners.

1. A GAS-BLAST ELECTRIC CIRCUIT-BREAKER COMPRISING FIRST AND SECONDCONTACT MEMBERS, SAID CONTACT MEMBERS BEING RELATIVELY MOVABLE BETWEENENGAGED AND DISENGAGED POSITIONS, SAID SECOND CONTACT MEMBER HAVING ANEXTERNAL CYLINDRICAL CONTACT SURFACE, AND SAID FIRST CONTACT MEMBERHAVING A PLURALITY OF CONTACT FINGERS DISPOSED IN A RING, SAID FINGERSBEING INDIVIDUALLY BIASED IN AN INWARD DIRECTION TRANSVERSE TO THEDIRECTION OF RELATIVE MOVEMENT OF SAID FIRST AND SECOND CONTACT MEMBERSSO AS TO ENGAGE, WHEN THE FIRST AND SECOND CONTACT MEMBERS ARE IN THEIRENGAGED POSITION, WITH SAID EXTERNAL CYLINDRICAL CONTACT SURFACE, ANAUXILIARY CONTACT MEMBER MOUNTED ON SAID FIRST CONTACT MEMBER WITHINSAID RING FOR LIMITED MOVEMENT RELTIVE TO SAID FIRST CONTACT MEMBER ANDLATERALLY DISPOSED WITH RESPECT TO AND ADJACENT TO SAID PLURALITY OFCONTACT FINGERS, MEANS AT LEAST TEMPORARILY TO BIAS THE AUXILIARYCONTACT MEMBER TOWARDS SAID SECOND CONTACT MEMBER WHEREBY THE AUXILIARYCONTACT MEMBER REMAINS PRESSED FIRMLY IN CONTACT WITH SAID SECONDCONTACT MEMBER DURING SEPARATION OF SAID FIRST AND SECOND CONTACTMEMBERS DURING OPENING OPERATION OF THE CIRCUITBREAKER, AND WHEREBY ONSEPARATION OF SAID PLURALITY OF CONTACT FINGERS FROM SAID EXTERNALCYLINDRICAL CONTACT SURFACE DURING SAID OPENING OPERATION SAID FINGERSMOVE TO MAKE CONTACT WITH THE AUXILIARY CONTACT MEMBER.